A first way that Doodle's brother is cruel is when he shows Doodle his coffin from when Doodle was an infant. Not only does the sight of a coffin scare a young child, but to consider that it was determined for Doodle himself made it that much more vulgar. He admits the cruelty in these lines:

One time I showed him his casket, telling him how we all believed he would die. When I made him touch the casket, he screamed. And even when we were outside in the bright sunshine he clung to me, crying, "Don't leave me, Brother! Don't leave me!"

A second way he demonstrates this cruelty happens in the very end. When Doodle's brother leaves him after it had started to rain, we see abandonment have dire, deadly consequences:

The rain came, roaring through the pines. And then, like a bursting Roman candle, a gum tree ahead of us was shattered by a bolt of lightning. When the deafening thunder had died, I heard Doodle cry out, "Brother, Brother, don't leave me! Don't leave me!"

The knowledge that our plans had come to nothing was bitter, and that streak of cruelty within me awakened. I ran as fast as I could, leaving him far behind with a wall of rain dividing us. Soon I could hear his voice no more.

This section shows that Doodle's brother understood his cruelty. It also demonstrates that each time Doodle's brother responded this way, Doodle interpreted the act as abandonment.

For a character in Doodle's condition, no greater affliction could be done to him by another than that, to be completely abandoned.